It is very typical in Japanese story telling (in many formats: novel, movie, drama, anime, manga, game, etc) that you don't need a reason WHY for things to be in such way in the story. They just are and needed for the story, so I learnt a long time ago not to ask question when enjoying these type of stories. Their strong point lies on the plot, characterization, emotion, etc.
Good example is Saikano/Saishu Heiki Kanojo: The Last Love Song on This Little Planet (in manga, anime and live action movie format)original by Shin Takahasi, 2005.